12 Hours
by Heaven Is A Book Shop
Summary: "Sure, every seventeen-year-old boy wants to spend twelve hours in bed with his girlfriend, but not every seventeen-year-old boy is at risk of burning, both, the bed and his girlfriend to smithereens..."
1. 12 Hours

**A/N: Hmm... I'm not sure this turned out how I had expected. I think it could be better but... hmm... Oh, I don't know. I just hope you enjoy it. :)**

**Usual Disclaimer Applies.**

* * *

**12 Hours**

_It may have been Izzy's idea, but it was all Brother Zachariah's fault._ That was Jace's conclusion as he lay with his back to the bathroom door. If it hadn't been for the Silent Brother wanting to test Jace's control of the Heavenly Fire he never would have been in this situation. He listened to Clary shuffling out of the en-suite and climbing into the bed. The bed they had to share for twelve hours. Sure, every seventeen-year-old boy wants to spend twelve hours in bed with his girlfriend, but not every seventeen-year-old boy is at risk of burning, both, the bed and his girlfriend to smithereens…

* * *

_Flashback_

_It had been earlier that day when Jace walked into the library, with Clary leaning heavily on him, the _iratzes_ still healing the scars a demon had given her._

_"Ah, Jace, Clary, we were just talking about you." Maryse's powerful voice cut through the room._

_Jace helped Clary, who was slightly delirious and _very_ sleepy, into the chair by the fire place, before turning to see the room. Brother Zachariah was sat at the table, next to Maryse, in one of the high backed chairs. Alec was stood in the corner of the room fiddling with his phone, that's all he ever did these days._

_"Ah," Jace began, "having your annual 'everyone knows Jace is the hottest person on the planet' meeting, are you?"_

It's biannual, actually. _The Silent Brother's voice echoed in his head._ And no, this is not that meeting.

_That woke Jace up, had Brother Zachariah just made a joke? That was creepy._

_Isabelle, who was leaning against one of the book cases, snorted. "In your dreams, Jace," Isabelle gave the grin she gave people when she knew something about them that they didn't. "We were actually discussing my _brilliant_ idea."_

_"Izzy, 'your ideas' and 'brilliant' do not belong in the same sentence. Much like 'your cooking' and 'edible'."_

_"Actually," Maryse interrupted. "It may not be the finest idea, but it's the best we've got."_

_"So, what is this '_brilliant_ idea' then?" Then something struck Jace, "An idea for what?"_

_There was something in Isabelle's sly smile that would make any man uncomfortable, but after living with her for seven years, Jace was immune to her cunning grins. "Well, Brother Zachariah is here to talk about the Heavenly Fire situation and suggested testing your control over the heavenly fire, which is when I came up with my _marvellous_ plan."_

_"So we've progressed from '_brilliant_ idea' to '_marvellous_ plan' now, have we?"_

_Maryse shifted uncomfortably at this point. "Well, using the new vision runes Clary created, we're going to watch the two of you…"_

_Clary had created vision runes which worked, basically, like CCTV cameras when drawn in the corner of a room. They could be watched from a larger "projection rune" as she called it which would be drawn on a large surface such as a wall or the floor, even a table._

_"Watch us?"_

_Isabelle's grin grew. "Yep, we're going to lock the two of you in your room for twelve hours, from nine tonight to nine tomorrow morning."_

_"And how is this supposed to test my control? Has Jocelyn even agreed to this?"_

_"I think you already know the answer to both those questions, Jace." Maryse did not break her calm stance._

_Of course he did. Even when Clary held Jace's hand they felt the jolt of fire run through his veins. Jace could do little more than give Clary a peck on the lips, without the risk of burning her. And Jocelyn knew that, she knew that if they spent a night in the same bed nothing would happen between them. Nothing _could_ happen between them._

_Jace stroked Clary's hair with the back of his fingers, as she slept like a kitten in the library armchair. "This is ridiculous. You know that, right?"_

_"Well, that may be but seeing the vision runes have already been drawn in each corner of your room, there's not much you can do about it now." It was rather unsettling that Maryse seemed so calm about this._

_Clearly, everyone thought he was in more control than he actually was. Just the other day he had almost singed Church's tail off. Jace had a feeling Isabelle's plan would go up in flames… literally._

_End of Flashback_

* * *

Now, here he was, lying in a bed with his back to his girl. The girl he would love in this lifetime, and the next.

"Jace?" Her soft voice whispered through the darkness and a cold hand touched his shoulder. She might not even have been that cold, but since waking up with the Fire his body seemed like it was in a permanent fever.

"Jace?" Clary asked again. "Jace, please look at me."

It was a bad idea, just looking at her sometimes made the fire in his veins burn up. And now, she was in his bed, wearing not much but an oversized t-shirt and some underwear, turning around would be a _very _bad idea.

Jace turned around and stared into her green orbs as she began to stroke his golden hair. "Jace, what's wrong?"

The golden boy's hands shook with the urge to hold her in his arms; it would be so easy to slip his arms around her soft waist. "I– I don't want to hurt you…"

_Why am I always so unsure of myself around her?_ He asked himself.

_Because you love her,_ an anonymous voice whispered.

"Oh, Jace" Clary gently pulled him towards her, allowing him to bury his face in her red curls. She kissed his temple and whispered, "I know you won't hurt me. Do you really think I would share a bed with you for twelve hours if I did think you weren't in control?"

"You greatly over estimate my self-control, Clary."

"Hey, look on the bright side. We get to be alone for once."

"Not really, they can still see us through the vision runes."

"Hmm…" Clary shifted slightly. "About that…"

Jace actually found himself smiling up at Clary. "Clary, what have you done?"

"It wasn't my fault! I haven't done anything! But they really should have asked if vision runes even worked in the dark before drawing them."

"So all they can see is…"

"Shadows," Clary finished for him, smiling. "There's no audio either."

"Perfect."

Forgetting everything he had warned himself of, Jace rolled over so he and Clary were pressed chest to chest. His hands were placed on Clary's supple waist, as her own hands ran up his bare chest and tangled themselves in his silky, fair curls. Her lips were tender as he gently kissed her and slowly she began to kiss him back harder…

Clary let out a faint cry, as she felt Jace's hands burn her waist. Jace was out of the bed like a rocket; even in only a pair of jogging bottoms the cold air didn't seem to affect him. He watched, helplessly, as Clary rolled up the too big t-shirt and was relieved to see he had done more damage to the shirt than her. Green met amber as she looked up and stretched out her arms towards him.

The blonde boy backed away from her, like a startled horse, until his back was against the wall. "No, no, Clary… No, I hurt you… I'm sorry… Clary…"

Wordlessly, the redhead clambered out of the bed, shivering in the cold and wrapped her arms around Jace's muscular waist. "It's ok, I'm ok… Shhh…" she comforted him as his passionate emotions caused his veins to burn. As Jace's golden body became hotter, Clary held him tighter, she could not let go. She could end up as a smouldering pile of ashes for all she cared, she would not leave him. "Shhh… Jace, I love you. You can do this, calm down."

She leaned on his chest as his body began to cool. Clary held his hand in a tight grip, when she stepped back to look at him slumped against the wall, panting with exhaustion. He squeezed her hand and whispered, "Thank you, Clary."

A gentle squeeze was all he needed to register that she understood.

Jace sensed Clary was about to pull him back towards the bed, "No, Clary–"

Clary cut him off before he could protest anymore, "Jace, you need to sleep, and with the state you're in I'm not going to let you sleep on the floor."

"But–"

She cut him off again, "But, you might hurt me again? Jace, you can barely stand, I don't think you even have the strength to hurt me."

Jace slowly let Clary guide him towards the bed, where he collapsed among the bed sheets. Clary pulled the covers over him and pushed the hair out of his face – a nurse tending her patient. Jace reached out to stroke her hair but instead placed his hand on his stomach and spoke feverishly, "Clary, I love you. I love you, Clary. You know that don't you? I love you…"

Clary found herself laughing (although she knew she shouldn't be), "Jace, I know you love me." She pressed her lips to his forehead, "I love you, too. Now, go to sleep."

She stayed up watching as he slept, stroking away the creases in his forehead. The mighty warrior had left a wondering, vulnerable boy searching for a loving touch. Clary sighed as she looked down at his hands that rested on his stomach, she often found herself wondering if they would ever get out of this, if they would ever be able to touch each other like they used to. But that was not something to be worrying about now.

Pressing a kiss on Jace's forehead and another on his cheek, Clary rested her head on his shoulder, so their noses were almost touching, and let herself be consumed by sleep.

* * *

**Well? What do you think? Review, please! :)**


	2. 12 More Hours

**A/N: This isn't how I expected it to be, kind of...**

**Usual Disclaimer Applies.**

* * *

**12 More Hours**

It was annoying. Whatever was tickling Jace's nose was annoying, even if it was soft and smelt of apples.

The shadowhunter opened his golden eyes blearily to see his room filled with intense daylight and a petite redhead curled up like a new-born kitten, a curtain of her hair spread over her face.

Careful not to wake the angel next to him, Jace slipped down the sheets to examine the burns from the previous night. The t-shirt bore blackened marks – as if Jace's hands had been covered in ink. It seemed ironic that demon blood was the destructor and yet the angel blood in his veins was powerless against the Heavenly Fire that burnt through almost anything that came into contact with his palms.

With another glance at the scorched shirt and the thought of Clary's reddened skin, Jace spoke aloud, "By the Angel, Jocelyn will kill me."

Unmoving from her snuggled position, Clary mumbled, "She'll have to get through me first."

Jace's speech became muffled as he nuzzled Clary's thick, red hair. "I'm sorry I woke you,"

Keeping her eyes firmly closed, Clary yawned, "Don't be. You'd have to wake me sooner or later – although I would have preferred later. And as for the burns – they'll be fine with a little moisturiser or a small _iratze_."

"But Jocelyn–"

"– Will be more annoyed about the t-shirt."

Sensing Jace's puzzled gaze, Clary explained, "I've been wearing it since I was twelve – mum's sentimental like that."

Jace tried to keep the smirk out of his voice as he asked, "You've had that t-shirt since you were twelve and it still doesn't fit you?" This effectively earned a punch in the shoulder from Clary, before she settled back into her peaceful sleep.

Fiddling with the ends of her crimson hair, Jace would have quite happily spent the rest of the morning watching the snoozing Clary. Isabelle, however, seemed to have other plans in mind as she burst through the door at nine o'clock on the dot.

"Morning, Lovebirds!" Isabelle cried as a Clary jumped into action, or at least as much action a freshly awoken Clary can handle. She immediately straightened up and pulled the covers around her body as if she had been caught bare.

_The burns, _Jace realised._ She doesn't want Isabelle to see how little in control I am._

_No, you _are_ in control, and Clary would kill you for thinking otherwise_, a voice as gentle as the wind whispered.

Still, he wrapped his arms protectively around Clary's slim waist, effectively covering the charred t-shirt.

"I have to say I'm quite surprised we didn't hear a peep out of the two of you _all_ night," Isabelle continued, pulling back the thin, white curtains. "Then again, I guess we'll never know what the two of you did last night, but maybe that's for the best…" Isabelle eyed the lack of clothing Jace wore.

Jace clenched his teeth, Isabelle knew as much as the next Institute resident that he could no longer hold Clary in the same way he used to – the way he yearned to as if his life depended on it.

Seeing the frustrated look in Jace's eyes, Isabelle made an excuse to leave – something about her (non-existent) annual spring clean – and scurried out of the room.

Running her fingers through his curls, Clary softly comforted Jace. "Ignore her. She's guessing – she has as much knowledge of what happened last night as anyone else."

Nestling into the red waves of Clary's hair, Jace hissed in a voice teeming with mischief, "Do you want to know what I'm thinking?"

"No," Was the immediate answer – a sensible answer, at that.

"Come on, Clary; consider it a thank you to Isabelle"

"No, Jace."

"A thank you for giving you a chance to spend twelve _glorious_ hours with _moi_," _Glorious_, probably wasn't the right word, but roasting or fiery didn't seem right either.

"It will only end in tears, probably yours when Izzy gets a hold of you."

"Consider it a chance to escape Izzy's cooking for a night."

"You've survived all these years, Jace, I think it's a bit late to start avoiding her food _now_."

"Please, Clary!"

Clary looked into Jace's molten eyes when she realised if she kept saying no, Jace would go ahead with his undoubtedly, reckless plan without her – now where would the fun be in that?

"Ok, what are you thinking?"

* * *

"Are you _sure_ that's safe?" Maia asked for the third time.

Jordan was sat next to her on the worn, coffee-stained sofa in Luke's bookshop, Clary and Jace sat on two equally tarnished chairs on the other side of a pile of dog-eared books they were "helping" Luke shelve.

Clary waved off her doubts, "It'll give him a chance to test his self-control."

"And it was Isabelle's '_marvellous_ plan' anyway; she just never expected it to be implemented on herself." Jace added.

Jordan leaned forward towards Jace and asked a question that he had wanted to ask since the plan was explained. "Will this affect… our own sleeping arrangements?"

Thus receiving a blush from Clary, and playful slap on the arm from Maia, who cried "Jordan!" in a scolding voice.

The werewolf just looked at his girl with an adoring expression that read, _Could you really blame me?_

Jace smirked at the couple's interaction, reminding him of a conversation similar to one he'd had with Clary about ducks and triple word scores, except he'd not really been _Jace_ then had he?

Shaking off the feeling of dread that chilled his bones at the thought of his possessed self, Jace turned back to Jordan. "Only if you sleep in there with them,"

With a wide smile, Jordan gazed at Maia, who was trying to hide her own grin. "We shouldn't,"

"Come on, May, you know you want to…"

Maia let a smile unfold across her face and with a final glance at Jordan she turned to the shadowhunters facing her. "Just this once,"

* * *

The vampire was stood in his cardboard box of a bedroom, when the door had flown open. He had stared at the shadowhunter as she was pushed through the door way like a piece of meat into a lion's den. He had ducked when the girl's inky hair had whipped around like a whirlwind. He had patiently listened as Isabelle Lightwood read out the note that had been pushed under the door. And he had cringed as he found his mini fridge was empty of the cold, lifeless blood.

The one thing Simon hadn't done was speak. What was there to say? He could be sarcastic like Jace, but something told him Izzy wouldn't appreciate that. Or he could try to be comforting, but Izzy wasn't the kind of girl to need comforting. Of course, he could always count down the seconds until nine o'clock tomorrow morning, but he didn't think _he_ could stomach that – let alone Izzy.

As if the life fell out of her body, Izzy flopped onto his unmade bed. "Well? Aren't you going to join me, or have you taken to sleeping in coffin, now?" Isabelle let a devilish smile creep across her face.

_I'm gawping_, Simon realised, _I'm gawping at the beautiful girl on my bed._

But now was not to the time to be gawping, or thinking about Isabelle on his bed. Now was the time for talking.

"Erm… er… I…" Simon stammered. _Wow, I sound like I've had my tongue cut out by faeries and fed to Church._

Isabelle raised a perfectly plucked eyebrow.

"Isabelle… you're not… concerned about being locked in my room?"

Shaking her hair like it was a dark cape, Isabelle shrugged; "I don't see why not, I knew Jace would try something like this, and Clary's just in for the ride–" She stopped when she saw Simon's expression. "–Maybe _ride_ wasn't the right word…"

Simon imagined he looked like he was sucking on sour lemons, "No, carry on. I _love_ talking about my friend's sex lives."

Isabelle smiled, "Y'know, I _swear_ Clary once said '_Sarcasm is the last refuge of the imaginatively bankru–'_"

Izzy glared at the wall when she was cut off by the peculiar sounds that had begun emerging from Jordan's room.

"Clary didn't have to live with Jordan and Maia." Simon reminded Izzy as he flopped onto the bed next to her. "Welcome to the Lewis-Kyle household, good luck trying to get some sleep around here."

* * *

Isabelle's midnight hair was spread over Simon's chest which, despite the fact they were both fully clothed, seemed rather intimate for 3am.

Simon couldn't remember waking up, but he couldn't remember sleeping either, and he, gladly, couldn't remember what time the noises from Jordan's room had stopped.

Watching the way Isabelle's back rose and fell with each breath, Simon back to the first time the met. His rat days seemed far behind him, thankfully, and so were the days he spent living in half fear, half admiration for Isabelle. Sadly, his days of Jace's insulting nicknames were not.

"Stop thinking," Isabelle mumbled into Simon's chest. "You're thinking so hard I can hear your thoughts…"

If Simon's heart was beating it would have skipped a beat, but it wasn't so it didn't.

"_Almost_, I'm not actually telepathic,"

Simon chuckled at this, "I guessed. I think I would have died long before I did if you were telepathic, Izzy."

_Might as well be honest with the girl, Simon_, "Rats, and Jace's nicknames, and… you."

Isabelle rested her hands under Simon's t-shirt before letting them wander up his chest. Her hot breath tickled his neck as she whispered, "Good, because I was thinking about you, too."

And Isabelle pressed her rouged lips to his.

The kiss was teasing like daring the other to pull away first, until Izzy rolled over, pulling Simon with her. Running her treacherous fingers through his hair, Isabelle pulled Simon down. Down until there was no space between them. No air. But you don't need air when you're a vampire, all you need is blood.

Simon pulled away as he felt his fangs rip through the soft skin of Isabelle's lips.

Seeing his fangs, Isabelle threw her hair over one shoulder and began unbuttoning her tight fitting shirt.

"No," Simon turned away from Isabelle, turned away from his only source of blood.

"Simon," Isabelle's voice was stern and a little frightening, as she turned Simon to look at her. "I am _not_ going through this again with you. Drinking blood is just part of who you are, like my Marks are just a part of me. There is nothing we can do to change that."

"You're runes are beautiful, Izzy"

"Stop," Izzy waved a long, slender finger in Simon's face. "Trying to change the subject, you need to do this Simon; there is no other way around."

Wrapping her arms around his neck, Isabelle pulled Simon closer. Her pale neck was so close; Simon could almost taste the blood. But before he pierced her skin, Simon let his lips glide over the smooth parchment of her neck and breathed, "Beautiful,"

Then Simon bit down into her flesh and let the warm, fresh blood fill his mouth.

* * *

**Reviews are welcome. :)**


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